Conductive shielding device

ABSTRACT

Devices and methods for reducing stray magnetic fields from an inductor are disclosed. In some aspects, a device includes a substantially U-shaped component configured to attach to a conductive surface of a printed circuit board and configured to substantially surround a lengthwise portion of an inductor on three sides of the inductor.

TECHNICAL FIELD

This patent application relates generally to a conductive shieldingdevice for reducing stray magnetic fields from an inductor.

BACKGROUND

An inductor can be constructed as a copper wire with a core wrappedaround it. The core can be formed of a ferromagnetic material andinclude an air gap. In operation, inductors generate a stray magneticfield. In some implementations, the inductor can be wrapped with aconductive band (e.g., a copper band) to reduce the stray magnetic fieldemitted from the inductor. Wrapping the inductor with a conductive bandis one way to reduce the stray magnetic field from the inductor;however, it can have disadvantages. For example, it can be difficult towrap the inductor with the conductive band.

SUMMARY

This patent application relates generally to a conductive shieldingdevice for reducing stray magnetic fields from an inductor.

In general, in one aspect, the invention features a method that includesattaching an inductor to a printed circuit board. The method alsoincludes attaching a U-shaped conductive shielding component to aconductive pad on the printed circuit board such that the conductive padand the U-shaped conductive shielding component substantially surround alengthwise portion of the inductor.

Embodiments can include one or more of the following.

Attaching the inductor to the printed circuit board can includeattaching the inductor such that a gap of the inductor is located on aportion of the inductor located adjacent to the printed circuit board.The U-shaped conductive shielding component can have a first sidesubstantially perpendicular to the printed circuit board, a second sidesubstantially perpendicular to the printed circuit board andsubstantially parallel to the first side, and a third side connected tothe first and second sides and substantially parallel to the printedcircuit board. The method can also include forming the U-shapedconductive shielding component using a metal stamping process. Attachingthe U-shaped conductive shielding component to the conductive pad on theprinted circuit board can include soldering the U-shaped conductiveshielding component to the conductive pad on the printed circuit board.

In general, in one aspect, the invention features a system for reducingstray magnetic fields from an inductor. The system includes a conductiveshielding device. The conductive shielding device includes a first side,a second side substantially parallel to the first side, and a third sideattached between the first and second side, the third side beingsubstantially perpendicular to the first and the second sides.

Embodiments can include one or more of the following.

The first side of the conductive shielding device can be substantiallyperpendicular to a surface of a printed circuit board. The second sideof the conductive shielding device can be substantially perpendicular tothe surface of the printed circuit board. The third side of theconductive shielding device can be substantially parallel to the surfaceof the printed circuit board. The system can also include a printedcircuit board. The printed circuit board can include a conductive pad ona surface of the printed circuit board. The conductive shielding devicefurther can also include a first attachment portion extending at anangle from the first side and a second attachment portion extending atan angle from the second side. The first attachment portion and thesecond attachment portion can be in electrical communication with theconductive pad. The conductive shielding device can be a stamped metalcomponent. The conductive shielding device can be formed of copper. Theconductive shielding device can be formed of tin. The system can alsoinclude an inductor attached to the printed circuit board. Theconductive pad, the first side of the conductive shielding device, thesecond side of the conductive shielding device; and the third side ofthe conductive shielding device can substantially surround a lengthwiseportion of the inductor.

In general, in one aspect, the invention features a device for reducingstray magnetic fields from an inductor. The device includes asubstantially U-shaped stamped metal component configured to attach to aconductive surface of the printed circuit board and configured tosubstantially surround a lengthwise portion of an inductor on threesides of the inductor.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Further features, aspects, andadvantages of the invention will become apparent from the description,the drawings, and the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a printed circuit board, an inductor, and ashield device with arrows indicating how they are interconnected;

FIG. 2 is a perspective view of the shield device of FIG. 1;

FIG. 3 is a top view of the shield device of FIG. 1;

FIG. 4 is a side view of the shield device of FIG. 1;

FIG. 5 is a side view of the shield device of FIG. 1;

FIG. 6 is a diagram of the metal pattern for the shield device of FIG.1;

FIG. 7A is a top view of an inductor;

FIG. 7B is a side view of the inductor of FIG. 2A;

FIG. 7C is a bottom view of the inductor of FIG. 2A;

FIG. 7D is an edge view of an inductor; and

FIGS. 8-16 show cross-sectional views of additional implementations ofthe shielding device.

Like reference numerals in different figures indicate like elements.

DETAILED DESCRIPTION

FIG. 1 shows an expanded view of a device 10 for shielding an inductor(hereinafter a “shielding device” or a “conductive shieldingcomponent”), an inductor core 11, a lead wire 18, and a printed circuitboard (PCB) 20. The lead wire 18 includes portions 17 a and 17 b thatextend from the inductor core 12 and form an electrical contact withcontact pads 22 and 26 on printed circuit board 20. Portions 17 a and 17b can also physically secure the inductor 12 to the printed circuitboard 20. The shielding device 10 is substantially U-shaped (e.g., has asubstantially U-shaped portion). The shielding device 10 can be attachedto the printed circuit board 20 such that the shielding device 10substantially encloses a length-wise portion (e.g., lengthwise portion13) of the inductor 12 on three sides and a conductive surface 24 on theprinted circuit board 20 substantially encloses a length-wise portion ofthe inductor 12 on a fourth side. When the shielding device 10 isattached to the conductive surface 24, the shielding device 10 andconductive surface 24 substantially surrounds a length-wise portion ofthe inductor 12. Since the combination of the conductive surface 24 andthe shielding device 10 form a conductive cylinder around thelength-wise portion of inductor 12, the stray magnetic fields from theinductor 12 can be reduced in comparison to an inductor without ashielding device.

In general, the shielding device 10 is formed of an electricallyconductive material. Exemplary conductive materials include copper, tinand beryllium-copper.

The use of the conductive surface 24 and the shielding device 10 toshield stray magnetic fields from the inductor 12 can provide variousadvantages. For example, since the shielding device 10 is attached tothe printed circuit board 20 to form a conductive perimeter around aportion of the inductor 12, the shielding device 10 can be applied usingsurface mount methods. In addition, since the shielding device 10 itselfdoes not need to be a closed structure, the shielding device 10 can beeasily made and assembled (e.g., as described below).

FIGS. 2-5 show a perspective view, a top view, and two side views of theshielding device 10, respectively. The shielding device 10 includesthree sides 30, 32, and 34 which, when attached to the conductivesurface 24 of the printed circuit board 20, form a U-shaped structurethat can surround a length-wise portion of the inductor 12. Sides 30 and34 may be substantially parallel to one another and side 32 connectedsides 30 and 34 and may be substantially perpendicular to sides 30 and34. Thus, when located on the printed circuit board 20, sides 30 and 34may be substantially perpendicular to a surface 21 of the printedcircuit board 20 and side 32 may be substantially perpendicular to thesurface 21 of the printed circuit board 20.

Side 30 of shielding device 10 can be of a height 36 and length 38. Side34 of shielding device 10 can be of a height 40 and length 42. In oneimplementation of shielding device 10, heights 36 and 40 and lengths 38and 42 may be substantially the same. In another implementation, heights36 and 40 and lengths 38 and 42 of the shielding device 10 may bedifferent. In one implementation, in order to accommodate the inductor12, heights 36 and 40 and lengths 38 and 42 are such that the inductor12 can fit within the shielding device 10. For example, heights 36 and40 can be from about 0.1 inch to about 1 inch and lengths 38 and 42 canbe from about 0.2 inches to about 2 inches.

Side 32 of shielding device 10 can be a width 44 and length 46. In oneimplementation of shielding device 10, lengths 38, 42, and 46 of theshielding device 10 may be substantially the same. In someimplementations, in order to accommodate the length and width inductor12, width 44 and length 46 are such that the inductor can fit within theshielding device 10. For example, width 44 can be from about 0.2 inchesto about 2 inches and length 46 can be from about 0.2 inches to about 2inches.

Shielding device 10 includes a pair of attachment portions 50 a and 50b. The attachment portions 50 a and 50 b extend from sides 30 and 34,respectively, and are used to attach the shielding device 10 to theconductive surface 24 of the printed circuit board 20. The attachmentportions 50 a and 50 b include regions 54 a and 54 b, respectively, thatmay be approximately perpendicular to sides 30 and 34. Thus, whenlocated on a printed circuit board, the attachment portions 50 a and 50b may be substantially parallel to the printed circuit board 20 formingboth a mechanical and an electrical connection between the shieldingdevice 10 and the conductive surface 24 of the printed circuit board 20.For example, the attachment portions 50 a and 50 b can be connected tothe conductive surface 24 of the printed circuit board 20 using aconductive adhesive (e.g., solder). Regions 54 a and 54 b can be of awidth 56. In one implementation of shielding device 10, in order tofacilitate attachment of the shielding device 10 to the printed circuitboard 20, the width 56 is such that the width 56 can cover a conductiveadhesive.

Shielding device 10 also includes two pairs of end tabs (e.g., end tabs60 a and 60 b and end tabs 62 a and 62 b). End tabs 60 a and 62 a extendat an angle from side 30 toward side 34. In some implementations, theend tabs 60 a and 62 a are substantially perpendicular to side 30.Similarly, end tabs 60 b and 62 b extend at an angle from side 34 towardside 30. In some implementations, the end tabs 60 a and 62 b aresubstantially perpendicular to side 34.

End tabs 60 a, 60 b, 62 a, and 62 b can be of a length 68. In oneimplementation of shielding device 10, length 68 is selected such that agap 64 is present between the end tabs 60 a and 60 b and between endtabs 62 a and 62 b. In some implementations, the width of the gap 64 canbe selected such that a portion of the lead wire 18 that extends fromthe core 11 of the inductor 12 can fit between the end tabs 60 a, 60 b,62 a, and 62 b without contacting the end tabs 60 a, 60 b, 62 a, and 62b.

It is believed that shielding device 10 can provide the advantage ofbeing easily manufactured. Since the shielding device 10 does not needto be a closed structure (e.g., because the fourth electricallyconductive side is provided by the conductive surface 24 of the printedcircuit board 20), the shielding device can be stamped from a sheet ofconductive material. For example, as shown in FIG. 6, a single piece ofconductive material can be bent to form shielding device 10. The pieceof conductive material is cut to form a rectangular portion 100 withfour smaller rectangular portions 102, 104, 106, and 108 extending fromthe rectangular portion 100.

Lines 110, 116, 118, 122, 126, 130, 134, and 138 indicate locations atwhich the single piece of conductive material is bent to form theshielding device 10. More particularly, the top surface 32 is formed bybending the piece of conductive material along lines 118 and 126 (asindicated by arrows 120 and 128). The sides 30 and 34 and attachmentportions 50 a and 50 b are formed by bending the piece of conductivematerial along lines 134 and 110 (as indicated by arrows 112 and 136).The end tabs 60 a, 60 b, 62 a, and 62 b are formed by bending the pieceof conductive material along lines 116, 122, 130, and 138 (as indicatedby arrows 114, 124, 132, and 140). Thus, shielding device 10 may beformed from a single cut piece of material by bending the material indesignated locations.

While implementations of the shielding device 10 have been describedabove, in general, the shielding device 10 having exemplary dimensionscan be customized for an inductor based on the dimensions of theinductor. In addition, the shielding device 10 can be used for bothsingle gap and dual gap inductors.

For example, FIGS. 7A-7C show a single gap inductor 141. In general, thesingle gap inductor 141 can be constructed as a lead wire 143 with acore 142 wrapped around the wire 143. The core 142 includes a slotthrough which the lead wire 142 extends. Portions 144 a and 144 b of thelead wire 142 extend outside the core 142 to form portions which areused to form an electrical contact with contact pads 22 and 26 (FIG. 1).The core 142 includes a gap 145. The gap 145 provides the inductanceeffect for inductor 141. In this example, the gap 145 is located on thebottom side of the inductor 141 and extends through the core 142 to theslot through which the lead wire 143 extends.

If an inductor having a single gap is used, a lengthwise portion of theinductor can be surrounded by the shielding device 10 and the conductivesurface 24 of the printed circuit board 20 such that the stray magneticfield from the inductor is substantially shielded. The inductor 141 canbe oriented within the shielding device as desired. For example, theinductor 141 can be oriented such that the gap 145 of the inductor 141is located on a portion of the inductor located adjacent to the printedcircuit board 20. In general, it is believed that the length of the gapof the inductor is proportional to the strength of the magnetic fieldgenerated by the inductor 141.

In order to reduce the stray magnetic field, in some implementations, itcan be beneficial to use an inductor having two gaps. FIG. 7D showsanother example of a dual-gap inductor 146 that includes a core 148 anda lead wire. In this exemplary inductor, the core 148 is formed of twocomponents that are attached. The locations at which the components areattached form the gaps. The inductor 146 having two gaps can be orientedwithin the shielding device as desired. For example, the inductor can beoriented such that the portion of the inductor between the two gaps islocated adjacent to the printed circuit board.

While implementations of the shielding device have been described abovein which the shielding device is formed of three sides connected to forma substantially U-shaped shielding structure, other substantiallyU-shaped arrangements are possible.

FIG. 8 shows a cross-sectional view of a implementation of a shieldingdevice 150 in which the shielding device 150 includes sides 154, 156,158, 160, and 162 that form a substantially U-shaped shield configuredto enclose a lengthwise portion of an inductor 12. As in theimplementations described above, when attached to a conductive surface24 on a printed circuit board 20 (e.g., using attachment portions 152and 164), shielding device 150 and the conductive surface 24substantially surround a lengthwise portion of the inductor 12.

FIG. 9 shows a cross-sectional view of an implementation of a shieldingdevice 170 in which the shielding device 170 includes sides 174, 176,178, and 180 that form a substantially U-shaped shield configured toenclose a lengthwise portion of an inductor 12. As in theimplementations described above, when attached to a conductive surface24 on a printed circuit board 20 (e.g., using attachment portions 172and 182), shielding device 170 and the conductive surface 24substantially surround a lengthwise portion of the inductor 12.

FIG. 10 shows a cross-sectional view of an implementation of a shieldingdevice 190 in which the shielding device 190 includes sides 194, 196 and197 that form a substantially U-shaped shield configured to enclose alengthwise portion of an inductor 12. As in the implementationsdescribed above, when attached to a conductive surface 24 on a printedcircuit board 20 (e.g., using attachment portions 192 and 198),shielding device 190 and the conductive surface 24 substantiallysurround a lengthwise portion of the inductor 12.

FIG. 11 shows a cross-sectional view of an implementation of a shieldingdevice 200 in which the shielding device 150 includes a single curvedportion 204 that forms a substantially U-shaped shield configured toenclose a lengthwise portion of an inductor 12. As in theimplementations described above, when attached to a conductive surface24 on a printed circuit board 20 (e.g., using attachment portions 202and 206), shielding device 200 and the conductive surface 24substantially surround a lengthwise portion of the inductor 12.

As shown in FIGS. 12-16, in some implementations, the attachmentportions can extend inward toward the center of the shielding device.

While implementations of the shielding device 10 have been described asshielding an inductor, shielding device 10 can be used to shield othertypes of devices. For example, shielding device 10 can be used to shielda transformer. In implementations where the shielding device 10 shield sa transformer, the shielding device 10 can be customized for thetransformer based on the dimensions of the transformer.

Elements of different implementations described herein may be combinedto form other implementations not specifically set forth above. Otherimplementations not specifically described herein are also within thescope of the following claims.

1. A method comprising: attaching an inductor to a printed circuit boardhaving a conductive pad, the inductor comprising a core component; andattaching a U-shaped conductive shielding component to the conductivepad on the printed circuit board such that: the conductive pad and theU-shaped conductive shielding component substantially surround alengthwise portion of the inductor; and the U-shaped conductiveshielding component at least partially covers the inductor and the corecomponent.
 2. The method of claim 1, wherein attaching the inductor tothe conductive pad on the printed circuit board comprises attaching theinductor such that a gap of the inductor is located on a portion of theinductor located adjacent to the printed circuit board.
 3. The method ofclaim 1, wherein the U-shaped conductive shielding component comprises:a first side substantially perpendicular to the printed circuit board; asecond side substantially perpendicular to the printed circuit board andsubstantially parallel to the first side; and a third side connected tothe first and second sides and substantially parallel to the printedcircuit board.
 4. The method of claim 1, further comprising forming theU-shaped conductive shielding component using a metal stamping process.5. The method of claim 1, wherein attaching the U-shaped conductiveshielding component to the conductive pad on the printed circuit boardcomprises soldering the U-shaped conductive shielding component to theconductive pad on the printed circuit board.
 6. A system for reducingstray magnetic fields from an inductor, the system comprising: a printedcircuit board having a conductive pad; a core component of the inductor,with the core component configured to attach to the conductive pad; anda conductive shielding device configured to at least partially cover thecore component when attached to the conductive pad, the conductiveshielding device comprising: a first side; a second side substantiallyparallel to the first side; and a third side attached between the firstand the second sides, the third side being substantially perpendicularto the first and the second sides.
 7. The system of claim 6, wherein:the first side of the conductive shielding device is substantiallyperpendicular to a surface of the printed circuit board; the second sideof the conductive shielding device is substantially perpendicular to thesurface of the printed circuit board; and the third side of theconductive shielding device is substantially parallel to the surface ofthe printed circuit board.
 8. The system of claim 6, wherein theconductive pad is on a surface of the printed circuit board.
 9. Thesystem of claim 6, wherein the conductive shielding device furthercomprises: a first attachment portion extending at an angle from thefirst side; and a second attachment portion extending at an angle fromthe second side.
 10. The system of claim 9, wherein the first attachmentportion and the second attachment portion are configured for electricalcommunication with the conductive pad.
 11. The system of claim 6,wherein the conductive shielding device comprises a stamped metalcomponent.
 12. The system of claim 6, wherein the conductive shieldingdevice comprises copper.
 13. The system of claim 6, wherein theconductive shielding device comprises tin.
 14. The system of claim 6,wherein the core component attaches the inductor to the printed circuitboard.
 15. The system of claim 6, wherein the conductive pad, the firstside of the conductive shielding device, the second side of theconductive shielding device, and the third side of the conductiveshielding device substantially surround a lengthwise portion of theinductor.
 16. A device for reducing stray magnetic fields from aninductor, the device comprising: a substantially U-shaped stamped metalcomponent configured to (i) attach to a conductive surface of a printedcircuit board, (ii) substantially surround a lengthwise portion of theinductor on three sides of the inductor, and (iii) at least partiallycover a core component of the inductor when the core component isattached to the conductive surface of the printed circuit board.